Abstract
Purpose: Spoken discourse analysis has gained empirical and clinical attention, yet current practice predominantly relies on picture-based tasks which may not fully capture the language impairments experienced by persons with aphasia (PWA) in more complex contexts. Expository discourse, though more cognitively demanding and structurally complex, remains under-researched in aphasia despite its ecological relevance. This study aimed to (1) compare nonverbal cognitive abilities in PWA and neurologically healthy adults (NHA); (2) examine the effects of discourse task by comparing expository and picture description performance in PWA; and (3) investigate associations between nonverbal cognitive abilities and discourse outcomes. Method: Participants (PWA = 24; NHA = 13) completed nonverbal cognitive tasks that assess processing speed, inhibitory control, and cognitive flexibility. They also completed expository discourse tasks (expressing opinions on the healthcare system and homeschooling). Discourse samples were analyzed using six variables (MATTR, Percent CIU, Verbs per utterance, syntactic complexity, local and global coherence) selected to represent linguistic, propositional, and macrostructural domains in discourse.Results: Significant group differences were found in cognitive flexibility task accuracy, and response times on tasks measuring cognitive flexibility and processing speed. In expository discourse, PWA performed worse than NHA across the linguistic, propositional, and macrostructural domains. Notably, task comparisons revealed that expository discourse elicited greater performance in syntactic complexity but poorer coherence than the picture description task in PWA. Cognitive influences on discourse differed by tasks and groups: in PWA, cognitive flexibility generally showed strong associations with all discourse domains across both tasks, with fewer correlations for the picture description task. Also, the pattern of associations varied across cognitive tasks and discourse measures for the picture description task. No significant associations were observed among controls. Conclusion: Findings highlight the unique interplay between cognitive and linguistic skills in the expository task. This finding supports the potential use of expository discourse in aphasia assessment.